1. Field of the Invention
The present invention relates to a recodable lever tumbler lock of the kind which comprises a plurality of spring-biassed lever tumblers which are pivotal about a respective pivot axle and which are provided at their ends distal from the pivot axle with an aperture or gate for receiving a leg of a fence which is mounted for rectilinear movement transversely to the direction of movement of the lock bolt. Each fence includes teeth which when coding the lock in conjunction with turning the key to bring the bolt to its locking or latching mode engages in a toothed coding device, wherein the legs of respective fences move out of the aperture or gate in the lever tumbler as the bolt moves to its locking position. The lever tumblers are returned to their original positions by respective springs, when turning of the key is completed.
If it is found necessary to recode the lock for some reason, for instance, to change the lever permutation because a key has been lost so that the lock can be operated with another key, the lock is first locked with the aid of a key which fits the current code, with the door of the safe deposit box held open so that the lock housing is accessible from inside the door. Subsequent to activating some type of latching device, the door is locked from the inside with the aid of the key, which normally has a greater turning angle than is permitted in the normal position of the latching device, whereupon the key is removed from the lock and the new key is inserted. The lever tumblers are recoded at the same time as the lock is brought to the locking mode with the aid of the new key, wherein said levers are lifted by the key bit (wards) to code positions different than those that were applicable to the key earlier used. At the same time, each lever tumbler pushes an associated fence transversely to the direction of bolt movement to a new position in which the fences are fixed in position with the aid of the coding devices during the final stage of bringing the lock to its locking mode.
The lock is therewith coded in accordance with the new key, which can be removed from the lock with the lock bolt in its outwardly projected locking position.
2. Related Art
Different types of related recodable or changeable lever tumbler locks are known to the art. For instance, U.S. Pat. No. 4,462,230 (Evans) teaches a lever tumbler lock in which a screw is rotated through a given number of turns by means of an appropriate tool in conjunction with coding the lock, after which the lock code is fixed by turning the screw in the other direction. There is a danger with this solution that the code will not be fixed satisfactorily if the screw is not tightened correctly.
Another drawback with this lock is that it is not compact enough and consequently it is possible to reach the lock mechanism and "feel" the mechanism with a steel wire or the like inserted into the lock housing.
U.S. Pat. No. 1,693,731 (Sioberg) teaches a similar, although slightly differently designed lock construction in which the latching element can be swung with the aid of a tool. In this case, the coding device coacts with a projection on a main lever tumbler. When the coding device is swung to one side, no engagement will take place between the coding device and the projection, therewith enabling the lock to be recoded.
This lock mechanism is also comparatively complicated and bulky, i.e. it suffers generally the same drawbacks as those encountered with the aforedescribed lock construction of Evans.
Further examples of the present standard techniques are found in U.S. Pat. No. 4,290,287 (Peppard) in which a pivotal latching device is used, U.S. Pat. No. 3,884,058 (Terry) in which the lock is not recodable and in which tumblers of alternating shorter and longer lengths are alternately used, DE-C 109,243 (Sommermeier) in which the coding device is comprised of pins which move parallel with the bolt, DE-A 2,800,539 (Kromer) in which the lock construction is not recodable, DE-C 389,133 (Hartlaub) which teaches a lock which comprises a number of lever tumblers that are able to swing in opposite directions and a number of apertured latching pins, and FR-A 2,663,072 (Comforti) which teaches a lock construction comprising mutually adjacent fences, each having a leg which engages a corresponding aperture or gate on a lever tumbler.
None of these known lock constructions can be considered to completely fulfil present-day demands for locks which are simple, reliable, compact and non-forcible.